China’s aviation regulator on Monday grounded nearly 100 Boeing Co 737 MAX 8 aircraft operated by its airlines, more than a quarter of the global fleet of the jets, after a deadly crash of one of the planes in Ethiopia.

However, a U.S. official said it was unclear what information the Chinese regulator was acting on because the investigation of Sunday’s crash, the second involving the latest version of the narrowbody jet, was in the early stages.

Speaking on condition of anonymity as the topic is sensitive, the U.S. official said there were no plans to follow suit, as the jet had a stellar safety record in the United States and there was a lack of information on what caused the Ethiopian crash.